Drafting machine



June 27, 1939. c. H. LITTLE DRAFTING MACHINE 5 Sheets-Sheet 1 Filed Feb. 15, 1956 INVENTOR. C/mmas /7( 4/7725 7 M, m gm ATTORNEYS June 27, 1939. c T E 2,164,217

DRAFTING MACHINE Filed Feb. 15, 1936 5 wa 2 Ill 7 g3 45 G) INVENTOR. Efi Y CHARLES h. 'L rns ATTORNEYS June 27, 1939. c H. LITITLE I 21mm? DRAFTING MACHINE Filed Feb. 15, 1936 5 Sheets-Sheet 3 H n 9 INVENTOR.

Cf/AFEZES LITTLE BY $4M, mafia;

ATTORNEYS June 27, 1939. H, 'Lm-LE 2,164,217

DRAFTING MACHINE Filed Feb. 15, 1936 5 Sheets-Sheet 4 INVENTOR. BY CHARLES hf LITTLE Mm am ATTORNEYS June 27, 1939. c. H. LITTLE DRAFTING MACHINE Filed Feb. 15, 1956 5 Sheets-Sheet 5 INVENTOR. CHAR; 15 /7." 07-745 ATTORNEYS Patented June 27, 1939 UNITED STATES PATENT OFFICE DRAFTING MACHINE Application February 15, 1936, Serial No. 64,140

2 Claims.

of parallelograms comprising wheels held in spaced relation by struts and operativelybonnected by flexible bands.

An object of the present invention is the provision of a novel, small, light, inexpensive drafting machine of the wheel and band type especially adapted for portable use.

Another object of the invention is the provision of a drafting machine of the wheel and band type comprising a band of novel construction,

including improved means for tightening the same,

Another object of the invention is the provision of a novel anchor for a drafting machine which can be readily adjusted along the upper edge of the drawing board as desired.

The present invention resides in certain novel details of construction and combinations and arrangements of parts, and further objects and advantages thereof will be apparent from the following description of the preferred embodiments described with reference to the accompanying drawings forming a part of this specification, in which similar reference characters designate corresponding parts throughout the several views and in which:

Fig. 1 is a plan of a drafting machine embodying the present invention;

Fig. 2 is an enlarged plan of the anchor end of the drafting machine shown in Fig. 1;

Fig. 3 is a section on the line 33 of Fig. 2, with portions in elevation;

Fig. 4 is a diagrammatic view of one of the bands;

Fig. 5 is a section on the line 5-5 of Fig. 3;

Fig. 6 is an enlarged plan of the elbow portion of the parallel motion arm of the drafting machine shown in Fig. 1;

Fig. 7 is a section on the line l'! of Fig. 6 with portions in elevation;

Fig. 8 is a plan view of the anchor strut;

Fig. 9 is a plan view of the protractor strut;

Fig; 10 is an enlarged plan of the protractor end of the drafting machine shown in Fig. 1;

Fig, 11 is a section on the line i l-I I of Fig. 10;

Fig. 12 is a section on the line l 2 l2 of Fig. 10;

Fig. 13 is a view similar to Fig. 3 showing a modified form of anchor;

Fig, 14 is a view similar to Fig. 6 showing a modified construction of elbow;

Fig: 15'is a section on the-line I5-l 5 of Fig. 14;;

Fig. 16 is a diagrammatic view showing a modifled form of band;

Fig. 1'? is a view similar to Fig. 8 showing a modified form of strut;

Fig. 18 is a view similar to Fig. 2 showing an anchor of further modified construction;

Fig. 19 is a section on the line I9I9 of Fig. 18;

Fig. 20 is a perspective view on the line 20-20 of Fig, 18.

Fig. 21 is a view similar to Fig. 20 but showing a modified construction;

Fig. 22 is a plan view with portions broken away showing a tool for adjusting the tension of the bands, in operating position;

Fig. 23 is a front elevation of the apparatus shown in Fig. 22; and

Fig. 24 is a section on the line 24-2d of Fig. 23.

While the drafting machines herein illustrated and described are the preferred embodiments of the invention, they are only illustrative thereof as the invention can be otherwise embodied, and I do not wish to be limited to the particular construction shown.

Referring to the drawings, the drafting machines shown therein comprise a parallel motion mechanism or arm provided at one end with an anchor for attachment to a drawing board or table and at the other end with a protractor assembly including rulers, etc. The parallel motion mechanism or arm consists of two parallelograms comprising flexible metal bands, designated generally by the reference characters A and B, encircling plastic wheels IO and II, and I2 and 13, respectively, of equal diameter and held apart or in spaced relation by struts preferably also made of a plastic and designated generally by the reference characters C and D.

The preferred construction of anchor is shown in Figs. 2 and 3 and comprises a plate-like member l5 adapted to rest upon the upper surface of the drawing board l6, and provided with a centrally located projection ll with which the wheel I2 of the anchor parallelogram is formed integrally. The member l5 has two projections l8 and 19 formed integrally therewith extending towards the rear and projecting downwardly in a manner to engage the rear edge of the board [6, and is detachably connected to the board by two C-clamps 20 and 2|, positioned in slots 22 and 23 opening into the rear of the projections I8 and I9. The C-clamps are retained in assembled relation with the projections l8 and I9 by pins 24 and 25 fixed in the clamps 20 and 2|. and projecting to either side thereof through elongated slots 26 opening into the underside of the projections.

The upper arms of the C-clamps are provided with thumb screws 21 and 28 threaded therein and engaging in suitable holes in the upper surface of the plate member l5, and the lower arms are provided with members 29 of U-shaped section adapted to engage the underside of the board. Preferably one of the screws 21 and 28 is threaded left hand instead of right hand. With the exception of the screws 21 and 28, the anchor is preferably made entirely of a plastic, and the construction is such that it can be readily adjusted along the upper edge of the board from the draftsmans position. After the screws have been rotated to release the clamps they can be used as handles in adjusting the anchor without removing the bands therefrom.

The wheel II at the elbow of the arm is held in spaced relation to the wheel II] by a strut A preferably molded in one piece of a plastic and comprising a rectangular member 36 having disk-like end sections 3| and 32, and provided with a downwardly projecting flange 33 extending entirely around the periphery thereof. As shown, the strut has a pan-shaped appearance and is reenforced by arcuate flanges 35 and 36 formed integral with the underside thereof adjacent the end sections 3l and 32, respectively. The upper disk-like end section 3| of the anchor strut C is pivotally connected to the anchor in axial alignment with the wheel 16 by a pivot pin 38 preferably made of metal molded therein, but may be made of a plastic, and which projects downwardly into a suitable aperture in the projection l1. Preferably the plastic from. which the projection I1 is formed contains some lubricating material, such as graphite, in the proportion of about 10% by weight of the whole, so that the bearing between the projection and the pin 36 is self-lubricating.

An alternative construction of strut wherein the central section is open, thus reducing the weight, is clearly shown in Figs. 17 to 20, inclusive. As shown in these figures the strut which is likewise preferably made of a plastic, consists of two disk-like end sections 40 and 4| connected by channel-shaped side rods 42 and 43 of inverted U-shaped cross-section formed integral therewith, For the purpose of strengthening the strut the inside flanges of the side rods 42 and 43 continue around the inside of the disklike end sections, forming thereon flanges 44 and 45, respectively, and the outside flanges continue around the ends of the strut forming outside flanges 45 and 41 on the end sections 40 and 4|, respectively, giving the end sections a cup-like appearance. A modified construction of the strut shown in Fig. 20 wherein the inside flange of the side rods is omitted, is illustrated in Fig. 21 which shows a section of side rod 48 so constructed. The struts C and D may be varied in construction from that shown as will be apparent from the foregoing, and the side rods where employed may be of any desired shape.

The wheel II of the anchor parallelogram and the wheel l2 of the protractor parallelogram, both of which are located at the elbow of the arm, are formed integral and rotatably supported in the lower disk-like end section 32 of the strut C through the medium of a cylindrical downwardly extending hub 50 formed integral with the underside of the strut C, to which they are secured by a screw 5|. The upper flange 52 of the wheel H and the lower flange 53 of the wheel l2 are formed separately, to simplify the molding process, and secured to the wheels in any convenient manner. In the event the strut C is made of metal the boss 50 about which the wheels are rotatably supported may be drawn up from the disk-like end section or made separately and secured thereto. It will also be apparent that the boss 50 may consist of a metal bushing molded in the strut. The band A which opera tively connects the two wheels l6 and H of the anchor parallelogram consists of a single cable 54 making two loops about the wheels, opposite ends of which are connected by a take-up in the form of a turnbuckle link 55. The parts of the band to which the turnbuckle link is threaded are provided with rectangular flanges 56 which prevent rotation thereof when the turnbuckle link 55 is turned. In the construction illustrated in Figs. 1 to 5, etc., rotation of the members 56 is prevented by the engagement of the second loop of the cable 54 in a slot 57 formed therein.

Fig. 1'7 illustrates a modified band construction wherein each of the two bands consists of a cable 58 making one complete turn about each wheel and only one loop therebetween. When a band of this construction is employed the members 56 must be operatively connected to the strut in some manner to prevent rotation thereof. This operative connection between the members 56 and the strut can be conveniently made by either employing a strut of the construction as shown in Figs. 18 to 20 or by forming an inside flange on the struts C and D to engage the members 56 therebetween and the outside flanges already on said struts.

In the preferred embodiment illustrated in Figs. 3 and 4, etc., the band A is secured to the wheels l and II by screws 59. This eliminates any possibility of the band slipping on the wheels and thus disturbing the alignment of the rulers. This arrangement also greatly reduces the tension required in the bands and in turn the load on the bearings, etc., without decreasing the accuracy. When it is desired to adjust the length of the cable by rotating the turnbuckle link 55, the screw 59 can be loosened temporarily, thereby permitting the cable to shift on the wheels and equalize the tension between the two loops thereof. The upper wheel I'll is provided with a flange 61, similar to the flange 52 on the wheel H, which assists in retaining the band in position thereon.

The protractor strut D as previously stated is likewise preferably made of a plastic and is similar in construction to the strut C but differs therefrom in some respects. Like the strut C it comprises a member 6|] provided with a reenforced disk-like end section 6| at the elbow of the arm, but instead of being on the upper side of the strut is on the lower side thereof and connected to the main part 60 by a flange 62 which extends entirely around the strut and an inside flange 63. A cylindrical hub 65 formed integral with the upper surface of the end section 6| projects into the lower end of the bore extending through the wheels II and I2 and is rotatably retained therein by the screw 51 which projects through the hub 50 and is threaded into a tapped aperture in the hub 65. The screw is provided with a shoulder which engages the end of the hub 65, leaving sufficient clearance between the head and shank of the screw and the strut C, to permit free rotation of the screw in the strut C and in turn the strut D and the wheels I l and [2.

The right hand or protractor end of the strut D has a downwardly extending reenforcing annular flange formed integral therewith and a distance below the band has a counterbore in its upper surface by virtue of which it is rotatably supported on the boss H. As shown the boss H is formed integral with the strut but may consist of a bushing molded therein. The rulers 13 and M which are also preferably made of a plastic are formed integral with the ruler plate 15 which has an enlarged boss 16 on the upper side thereof extending into a counterbore in the underside of the hub of the wheel l3. A protractor plate I! also preferably made of a plastic and provided with the usual graduations is interposed between the ruler plate and the hub of the wheel l3 and secured to the wheel by screws 18. The ruler assembly including the ruler plate 15- and the rulers l3 and 14 is held in assembled relationship to the wheel [3, and in turn the wheel I3 is held in assembled relationship with the boss H and the strut D, by a pin or shaft 89 molded into the boss 16 and projecting upwardly through the center of the wheel l3 and the boss H, and terminating above the strut D where it is provided with a hand wheel Bl preferably made of a plastic secured thereto as by a set screw 82.

The periphery of the protractor plate 11, which is preferably made of a plastic. is of reduced thickness and is adapted to be clamped to the ruler assembly to secure the latter in any adjusted position by a clamp member 85, preferably made of a plastic, one end of which is undercut and overlies the reduced periphery of the protractor plate, while the other end bears against and is fulcrumed on the upper surface of the ruler plate. The clamp member is adapted to be actuated to clasp the periphery of the protractor plate therebetween and the upper surface of the ruler plate by a winged nut 86 threaded onto the upper end of a screw 81 secured in the ruler plate and projecting through an aperture in about the center of the clamp member. A dead line mark 88 for the protractor is provided on a member 89 also preferably made of a plastic carried by the ruler assembly outside of the protractor. The inside end of the member 89 is undercut so that it overlies the reduced periphery of the protractor and locates the dead line mark adjacent to the graduations on the protractor plate. If desired, the protractor plate can be omitted and the ruler assembly including the rulers and the ruler plate can be formed integral with the wheel l3. This construction does not permit the rulers to be angularly adjusted relative to the wheel l3 but results in a lighter and less expense machine suitable for many purposes.

Fig. 13 shows a modified construction of anchor, also preferably made of a plastic, especially adapted for use with comparatively thin boards. As shown in this figure, the plate-like member 94 with which the projection 95, similar in construction to the projection I! of the preferred embodiment, is formed integrally, has a plurality of rearwardly and downwardly extending projections 96 adapted, to engage the rear edge of the board 91, and is held in engagement with the upper surface of the board by a plurality of spring clamps comprising flat spring members 98 bolted to the upper side thereof and extending around the rear of the board and engaging underneath the same. A plurality'of tongues or projections 99 on the under surface of the member 94 whichengages in slots or grooves formed in the upper surface of the board retain the anchor in assembled relation with the board during operation of the machine but permit it to be readily and quicklyshifted along the rear edge of the board or removed therefrom.

Another modified construction of anchor, also preferably made of a plastic, is shown in Figs. 18 and 19 which show the anchor end of a drafting machine employing struts of the construction shown in Fig. 17 and the band arrangement shown in Fig. 16. As shown in these figures, the projection I95, which corresponds to the projection ll of the preferred embodiment, is formed integrally with a channel-shaped bracket I06 adapted to engage over the rear edge of the board l9! which is clamped thereto between the lower flange I98 of the bracket and a plate I99 located between the upper surface of the board and the top flange of the bracket. The plate I09 is adapted to be raised and lowered by a plurality of screws HIJ threaded into suitably tapped apertures in the upper flange of the bracket I 96 the lower ends of which are rotatably secured in the plate I99. The upper ends of the screws H9 which extend above the upper flange of the bracket are provided with knobs III for manual operation thereof. One of the screws H9 is preferably threaded left-hand instead of righthand to facilitate operation thereof.

A tool especially adapted for rotating the turnbuckle links 55 of the machine shown in Figs. 18 and 19, while the bands are in position, and thus adjusting the tension thereof, etc., is shown in Figs. 22, 23 and 24. The tool designated in general by the reference character E, comprises a wrench proper and a guide member therefor. The wrench proper consists of a socket formed by two members H5 and H6 secured to an arcuate shaped end of a handle H1. The guide member is made from a single piece of sheet metal and comprises a central trough or arcuate shaped section H8 within which the arcuate shaped end of the wrench is adapted to rest and slide. The section H8 of the guide member is considerably longer than the wrench is wide and the wrench is adapted to be engaged and disengaged with the hexagonal portion of the turnbuckle link 55 by sliding the same longitudinally of the band. At opposite ends of the central section H8 the guide member is provided with upstanding prongs H9 which form spring clips within which the rods are engaged. Beyond the prongs H9 end sections I20 are provided for preventing the tool from rocking on the drawing board or surface upon which it is supported. In operation the guide member is pushed under the side rod with the prongs or clips H9 engag ing the flanges thereof, after which the wrench proper is inserted underneath the side rod and engaged with the hexagonal section of the turnbuckle line 55.

Certain advantages are to be obtained by being able to adjust the tension of the bands by changing the operating center to center distance of the wheels rather than by adjusting the length of the band, since when a take-up is employed in the band any adjustment thereof produces an angular movement of the rulers. Preferably both means of adjusting the tension should be incorporated in each machine as the take-up in the band is desirable for initially tightening the band and later for producing an angular adjustment of the rulers if desired. Usually an adjustable strut increases the size, weight, and cost of the drafting machine and one of the objects of the present invention is the provision of such a construction which will be light in weight, rugged in construction, and inexpensive to manufacture, and which will not materially or objectionably increase the size of the machine.

Such a construction is shown in Figs. 14 and 15 which correspond to Figs. 6 and 7 of the preferred embodiment and show a modified construction of the elbow portion of the arm of the machine shown in Figs. 1, 2, etc. Referring to these figures of the drawings, the strut I25 shown therein corresponds to the strut C in the preferred embodiment and is similar thereto in construction except for the fact that the disklike end section I26 at the elbow end is comparatively flat on top and provided with a cylindrical aperture counterbored from the under side. The wheels II and I2 instead of being directly connected to the strut, as shown in the preferred embodiment, are rotatably fixed to a cylindrical hub I28 corresponding to the hub 50, but formed integrally with a member I29 secured in the aperture in the strut and rotatably adjustable therein about an axis eccentric to the axis of the hub I28. A wear plate I30 preferably made of a plastic containing a lubricant such as graphite is interposed between the wheels and the member I26.

The anchor strut I32 is similar in construction and is rotatably supported about the axis of the wheels by a member I33 secured in the aperture therein and angularly adjustable about an axis eccentric to the axis of the wheels. From the foregoing description it will be apparent that the operating center to center distance of the wheels of the anchor parallelogram can be varied by rotating the member I26 in the strut, and that the operating center to center distances of the wheels of the anchor parallelogram can be varied in a like manner by rotating the member I33 in the anchor strut I32. It is to be understood that the eccentrics need not be located at the elbow of the arm but such is the preferred construction.

From the foregoing description of the preferred embodiment of the invention it will be apparent that a new and inexpensive drafting machine has been provided. The drafting machine for the most part is preferably made of a plastic, for example, a polymerization product of a vinyl compound such as vinyl chloride, vinyl acetate, or vinyl benzine. The bands are preferably made of steel cables of the type known commercially as aeroplane cable, and encircle the wheels as illustrated. The arrangement of bands shown in combination with plain bearings is especially suited to small machines, that is, machines in which the arm is from twelve to twenty-four inches in length. In larger machines it is advisable to use anti-friction bearings.

While the preferred embodiment of the invention has been illustrated and described, I do not wish to be limited to the particular construction shown, which may be Varied within the invention, and I particularly point out and claim as my invention the following:

1. A drafting machine comprising a parallel motion mechanism, said parallel motion mechanism comprising a pair of wheels, a flexible band operatively connected to said wheels, a strut made of a plastic, a member rotatably connected to one end of said strut, and means for operatively connecting one of said wheels with said member with the axis thereof eccentric to the axis of rotation of said member.

2. A drafting machine comprising: a parallel motion arm, a protractor assembly mounted on one end of said arm, an anchor at the other end of said arm for detachably connecting said arm to a drafting board or the like, said anchor comprising a bracket connected to said arm and constructed to engage the top and rear surfaces of said board, and a channel-shaped clamped member adapted to engage over said bracket and the edge of the board and having a screw extending normal to the working surface of the board for clamping said bracket to the board.

CHARLES H. LITTLE. 

